Hail!
The first time I read about a Mimir was on the "Player's Guide to the Outlands", where a perticular Mimir wisdom is on a audio CD (it was the only audio CD product for Planescape).
IIRC, a Mimir just has some recorded descriptions, and an vocal "interface". It is like a lot of interviews and a librarian to search among them.
If you do not want to specify exactly what information was recorded on it, you may try using it as the bard lore ability (the answers are provided in the form of a recorded interview/testimony).
I hope it was useful.
bye,
heylel.